Neural Correlates of the Antinociceptive Effects of Stimulating the Anterior Pretectal Nucleus in Rats

  • Karina Genaro
    Department of Neuroscience and Behavioral Science, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil

    Institute of Neuroscience and Behavior—INeC, Ribeirão Preto, São Paulo, Brazil
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  • Wiliam A. Prado
    Address reprint requests to Wiliam A. Prado, MD, PhD, Department of Pharmacology, Ribeirão Preto Medical School, Av Bandeirantes 3900, CEP 14049-900, Ribeirão Preto, SP, Brazil.
    Institute of Neuroscience and Behavior—INeC, Ribeirão Preto, São Paulo, Brazil

    Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
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Published:August 03, 2016DOI:


      • Stimulation of the anterior pretectal nucleus (APtN) evokes antinociception in rats.
      • Stimulation of APtN activates two descending pathways.
      • One APtN pathway relays in the ipsilateral lateral paragigantocellular nucleus.
      • Other APtN pathway relays sequentially in two mesencephalic nuclei.


      Stimulation-evoked antinociception (SEA) from the anterior pretectal nucleus (APtN) activates mechanisms that descend to the spinal cord through the dorsolateral funiculus, but the encephalic route followed by the descending pathways from the APtN is not completely known. This study evaluated the changes in the SEA from the APtN in the Wistar rat tail-flick test after lidocaine-induced neural block or N-methyl-d-aspartate-induced neurotoxic lesion of the deep mesencephalic nucleus (DpMe), tegmental pedunculopontine nucleus (PPTg), or lateral paragigantocellular nucleus (LPGi). The SEA from the APtN was less intense after neural block of the contralateral DpMe or PPTg or the ipsilateral LPGi, but was not changed by the neural block of the ipsilateral DpMe or PPTg or the contralateral LPGi. Antinociception did not occur when APtN stimulation was carried out 5 minutes after lidocaine or 6 days after N-methyl-d-aspartate injections into the contralateral DpMe and the ipsilateral LPGi, or into the contralateral PPTg and the ipsilateral LPGi. We conclude that the SEA from the APtN activates 2 descending pain inhibitory pathways, one relaying in the ipsilateral LPGi and another relaying sequentially in the contralateral DpMe and PPTg.


      The antinociceptive effect of the APtN stimulation involves 2 descending pathways: one relaying in the ipsilateral LPGi and another descending contralaterally via relays in the DpMe and PPTg.

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